JPH0587024A - Air intake device of engine - Google Patents

Abstract

PURPOSE:To attempt compatibility between promotion of fuel carburetion/ atomization caused by fuel injection to high flow speed intake air, and improvement of filling efficiency caused by high level maintenance of average flow speed, and also achieve improvement of scavenging property or the like simultaneously, in the air intake device of a fuel injection type engine provided with an air intake passage having a curved part. CONSTITUTION:The air intake device of an engine is provided in such constitution that an injector 25 is arranged in an air intake passage 12 having a curved part 13, and also an appropriate quantity of additional gas G is supplied into the intake passage 12. The injection hole 26 of the injector 25 is opened to the curved part 13 of the intake passage 12, or to the immediately downstream position of the curved part 13, and also on the wall surface 13a on the outer circumference side of the curved part 13. On the other hand, the injection part 36 of aditional gas G is opened on the wall surface 13b on the inner circumference side of the curved part 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine intake device.

[0002]

2. Description of the Related Art In a fuel-injection engine equipped with an injector, fuel is directly injected and supplied into the intake passage, so that the vaporization / atomization performance of the engine greatly affects the combustion performance of the engine and the output performance. Affect. Therefore,
Conventionally, various ideas for promoting vaporization and atomization of injected fuel have been proposed. One of them is to inject the fuel from the injector to a portion of the intake passage where the intake flow velocity is the fastest and to obtain intake air and fuel. To promote the mixing of
There is an idea to improve atomization. As means for embodying such an idea, for example, as disclosed in Japanese Patent Laid-Open No. 20624/1987, the intake passage is formed in a curved shape, and the injection hole of the injector is formed. It is known that the curved portion is opened on the outer peripheral side wall surface so that fuel is injected into the intake air flow having a high flow velocity near the outer peripheral side wall surface.

Incidentally, it is generally known that the flow velocity distribution of the fluid (for example, intake air) flowing in the curved passage has a distribution state in which the high flow velocity region is biased toward the outer periphery thereof as shown in FIG. , This is due to the influence of the secondary flow due to the inertial force of the intake flow. That is, since the intake flow A flowing in the curved passage 51 tends to flow linearly due to its inertial force (in other words, it tends to flow toward the outer peripheral wall 51a side of the curved passage 51), the curved passage When 51 is viewed from the cross-sectional direction, it flows from the inner peripheral wall 51b to the outer peripheral wall 51a along the planes on both sides of the plane including the central axis of the curved passage 51, then reverses to form side peripheral walls 51c, 51c. A secondary flow A'flowing from the outer peripheral wall 51a side to the inner peripheral wall 51b side is generated along the line. When such a secondary flow occurs in the curved passage 51, the flow velocity distribution in the axial center direction which should be symmetrical with respect to the passage axial center is deformed by the secondary flow, and as a result, as shown in FIG. In addition, the flow velocity distribution is such that the high flow velocity region is biased toward the outer peripheral wall 51a.

[0004]

By the way, in the intake passage having such a curved portion, as described above, the high flow velocity region is biased toward the outer periphery thereof, so that if the fuel is injected into this portion, the fuel is mixed. Although it is promoted and its vaporization / atomization performance is good, on the other hand, it has been pointed out for some time that the bias of the flow velocity distribution impedes the intake charging efficiency. That is, when the high flow velocity region in the curved passage 51 is largely deviated to the outer peripheral wall 51a side as described above, the maximum flow velocity of the intake air is increased, but the average flow velocity is relatively low. This means that the effective cross-sectional area of the curved passage 51 is not fully utilized, and as a result, the charging efficiency of the intake air becomes relatively low relative to the effective cross-sectional area of the curved passage 51. is there.

In order to increase the average flow velocity of intake air and improve its charging efficiency, it is sufficient to make the intake passage as straight as possible. In such a case, however, the maximum flow velocity decreases. As a result, there is a problem that the mixing performance of fuel deteriorates and the overall height of the engine increases, which hinders the compactness of the engine.Therefore, the curved intake passage is adopted in consideration of the above advantages and disadvantages. The current situation. Therefore, under the present circumstances, it is considered that the reduction of the filling efficiency is an unavoidable matter as long as the curved intake passage structure is adopted, but when considering the engine performance from a total point of view, the intake passage having the curved structure is provided. However, the decrease in filling efficiency cannot be overlooked, and a solution to it is awaited.

In view of the above, the present invention is directed to promoting the vaporization and atomization of fuel by injecting fuel into high-velocity intake air and maintaining a high average velocity in an intake system for a fuel injection engine having an intake passage having a curved portion. It was achieved with the aim of achieving both improvement of filling efficiency and improvement of scavenging performance at the same time.

[0007]

BACKGROUND OF THE INVENTION In the process of researching means for solving such a problem, the inventors of the present invention have adopted a basic structure in which intake air is flown in a curved passage. Recognizing that the biasing phenomenon toward the outer peripheral wall side is unavoidable, we changed the viewpoint from the technological development to improve the biased flow velocity distribution peculiar to curved passages.
It was decided to develop a technique to increase the average flow velocity while maintaining the maximum flow velocity caused by the deviation of the flow velocity distribution at a high level with almost no decrease. And
Here, we paid attention to the deviation of the intake dynamic pressure and the characteristics of the secondary flow due to the deviation of the flow velocity distribution.

That is, as shown by the flow velocity distribution curve L ₁ in FIG. 4, the intake air flowing in the curved passage 51 has a high flow velocity region in the outer peripheral wall 51.
The flow velocity distribution is biased to the side of a, but this is because of the intake dynamic pressure, the outer peripheral wall 51a of the curved passage 51
It is attributed to the fact that the dynamic pressure is high in the side portion and the dynamic pressure is low in the inner peripheral wall 51b portion. Therefore, if the additional gas injection port 52 is formed on the side of the inner peripheral wall 51b having such a low dynamic pressure and the additional gas G for intake air such as EGR gas is supplied from this, the additional gas G has a low dynamic pressure. The additional gas G that is smoothly sucked and introduced into the vicinity of 51b is introduced to the downstream side by the intake flow flowing in the curved passage 51, and is added to the original intake flow velocity distribution. As shown by the flow velocity distribution curve L ₂ , a new high flow velocity region is formed in the portion of the original intake flow velocity distribution curve closer to the inner peripheral wall, and the flow velocity distribution curve L ₂ as a whole is divided into a portion closer to the outer peripheral wall and a portion closer to the inner peripheral wall. It becomes a "two-hump camel" -like curve having a high flow velocity region on both (in the flow velocity distribution curve L ₂ ,
The part indicated by the broken line arrow is the flow velocity added by the additional gas).

When the intake gas and the additional gas having such a "two-hump camel" -shaped flow velocity distribution flow further downstream,
The flow velocity portion added by the additional gas due to the secondary flow generated in the curved passage 51 is gradually pushed out from the inner peripheral wall 51b side to the outer peripheral wall 51a side, whereby the flow velocity distribution is gradually averaged and finally the flow velocity distribution curve. maximum flow rate as indicated by L ₃ are those flow velocity distribution of the substantially trapezoidal velocity itself is averaged in a state where almost no decrease, i.e. high flow velocity distribution of the average flow velocity is obtained.

Based on such knowledge, the inventors of the present invention maintain both the maximum flow velocity and the average flow velocity at a high level by introducing the additional gas to the inner peripheral wall side of the curved passage, and thus, to the high flow velocity region. The present invention is based on a technical idea for simultaneously improving the mixing performance by fuel injection and the intake charging efficiency by a high average flow velocity.

[0011]

Based on such background art, as a concrete means for solving the above problems in the present invention, in the invention according to claim 1, an injector is arranged in an intake passage having a curved portion. In addition, in the intake device of the engine adapted to supply an appropriate additional gas into the intake passage, the injection hole of the injector is provided at the curved portion of the intake passage or at the curved portion immediately downstream of the curved portion. While being opened on the wall surface on the outer peripheral side of the above, the ejection portion of the additional gas is opened on the wall surface on the inner peripheral side of the curved portion.

According to the second aspect of the present invention, the injector is arranged in the intake passage having the curved portion, and the on-off valve which selectively opens and closes the intake passage upstream of the injector according to the operating condition of the engine. In the intake system for an engine, the injection hole of the injector is opened on the wall surface on the outer peripheral side of the curved portion, while the on-off valve is a butterfly valve and the valve axis direction thereof is the curved portion. Is arranged in the vicinity of the upstream end of the bending portion in a direction orthogonal to the bending surface direction, and when the valve is opened, the peripheral portion located on the outer peripheral side of the bending portion is located on the inner peripheral side. It is characterized in that the valve opening operation direction is set so as to be located on the intake downstream side of the section.

According to a third aspect of the present invention, in an engine intake device in which an injector is arranged in the intake passage and an appropriate additional gas is supplied into the intake passage, the intake passage has the upstream side thereof. Located at the upstream side of the engine and curved to wrap around from the upper side to the side of the engine, a straight line portion that linearly extends obliquely downward continuously to the downstream end of the upstream side bend portion, and a downstream side of the straight line portion. The intake port is continuous with the end and bends in the direction opposite to the upstream bending portion.
And a downstream side curved portion communicating with the upstream side curved portion, the injection hole of the injector is opened on an axial extension of the straight line portion, and the additional gas jetting portion is formed on the inner circumference of the upstream side curved portion. The feature is that it is opened on the side wall surface.

According to a fourth aspect of the present invention, in an engine intake device in which an injector is arranged in the intake passage and an appropriate additional gas is supplied into the intake passage, the intake passage has the upstream side thereof. Located at the upstream side of the engine and curved so as to wrap around from the upper side to the side of the engine, a straight line portion that linearly extends continuously to the downstream end of the upstream side bend portion, and a continuous portion to the downstream end of the straight line portion. And a downstream side curved portion which is curved in a direction opposite to the upstream side curved portion and communicates with the intake port, and further, the injector.
Of the additional gas is opened on the inner peripheral side of the upstream curved portion while the injection hole of the additional gas is opened on the wall surface of the upstream curved portion or the straight portion and corresponding to the outer peripheral side of the upstream curved portion. It is characterized by opening on the corresponding wall surface.

According to the fifth aspect of the present invention, the injector is arranged in the intake passage having the curved portion, and an appropriate additional gas can be supplied into the intake passage, and further upstream of the injector. Is an engine intake device in which an opening / closing valve for selectively opening and closing the intake passage is arranged according to the operating state of the engine.
To open the injection hole on the curved portion of the intake passage or on the wall surface on the outer peripheral side of the curved portion immediately downstream of the curved portion,
Further, while the injection portion of the additional gas is opened on the wall surface on the inner peripheral side of the bending portion, the on-off valve is constituted by a butterfly valve and its valve axis direction is orthogonal to the bending surface direction of the bending portion. And is set in the vicinity of the upstream end of the curved portion in a state of being directed toward the direction, and when the valve is opened, the peripheral portion located on the outer peripheral side of the curved portion is on the intake downstream side of the peripheral portion located on the inner peripheral side. It is characterized in that the valve opening operation direction is set so as to be located at.

According to the sixth aspect of the present invention, an injector is arranged in the intake passage so that an appropriate additional gas can be supplied into the intake passage, and further upstream of the injector depending on the operating condition of the engine. In an intake device for an engine having an opening / closing valve that selectively opens and closes the intake passage, an upstream bending portion that is located on the upstream side of the intake passage and bends so as to wrap around from the upper side to the side of the engine. A straight line portion continuously extending in a straight line at the downstream end of the upstream side curved portion and a straight line portion continuous with the downstream end of the straight line portion and curved in a direction opposite to the upstream side curved portion to communicate with the intake port. On the other hand, the injection hole of the injector is opened along the axial extension of the straight portion, and the injection portion of the additional gas is formed on the inner peripheral side wall surface of the upstream bending portion. Open to Further, the on-off valve is configured as a butterfly valve, and is arranged and set in the vicinity of the upstream end of the bending portion with the valve axis direction thereof being oriented in a direction orthogonal to the bending surface direction of the bending portion, and the opening and closing thereof is performed. It is characterized in that the valve opening direction is set so that the peripheral edge portion located on the outer peripheral side of the curved portion is located on the intake downstream side with respect to the peripheral edge portion located on the inner peripheral side during valve operation.

According to the invention described in claim 7, claims 1, 3.
In the intake system for an engine according to 4, 5 or 6, assist air can be supplied to the vicinity of the injection hole of the injector through an assist air passage, and the additional gas passage for supplying the additional gas is provided in the assist air passage. It is characterized in that they are arranged side by side in close proximity to the passages, and that the assist air passage and the additional gas passage are formed so as to straddle between the intake passages of each cylinder.

[0018]

With each of the inventions of the present application, the following effects can be obtained by adopting such a configuration.

According to the first aspect of the present invention, the intake flow flowing through the intake passage due to the operation of the engine is caused by the inertial force of intake air at the curved portion because the intake passage has the curved portion. Due to the influence of the secondary flow, the flow velocity distribution exhibits a flow velocity distribution in which the high flow velocity region is biased toward the wall surface portion on the outer peripheral side of the curved portion. Therefore, by injecting the fuel from the injector in such a high flow velocity region, the mixing between the intake air and the fuel becomes good, and the vaporization and
Atomization is promoted. Further, when the fuel is injected into the high flow velocity region in this manner, the fuel is carried on the high-velocity intake air flow and is smoothly carried to the downstream side, so that the fuel is less likely to adhere to the passage wall surface. If the responsiveness of the engine output to the fuel supply is good, it is possible.

On the other hand, since the inner peripheral side of the curved portion has a relatively low flow velocity, the dynamic pressure thereof is low, and by supplying the additional gas from the ejection portion provided at the portion where the dynamic pressure is low, The additional gas is smoothly sucked and introduced by the intake air flow flowing in the curved portion, and is added to the intake air flow while being pushed by the intake air flow, so that the flow velocity on the inner peripheral side is increased. Then, the additional gas introduced to the inner peripheral side and added to the intake air flow is extruded to the outer peripheral side by the secondary flow generated in the curved portion, so that the flow velocity distribution in the curved portion is averaged, thereby The average flow velocity in the intake passage is increased.

As described above, when the average flow velocity in the intake passage is increased (in other words, the flow velocity distribution is changed), this influence extends to the upstream side portion and the average flow velocity in the upstream side portion is also increased. It will be raised.
Due to such an improvement in the average flow velocity, the intake air is efficiently introduced in a wider range of the intake passage (in other words, the utilization efficiency of the effective sectional area of the intake passage is improved), and the intake air The filling efficiency can be improved.

Further, since the additional gas is introduced near the inner circumference of the curved portion, when the curved portion is viewed from the cross-sectional direction,
As described above, although there is the action of moving the additional gas by the secondary flow, the density of the additional gas is high on the inner peripheral side and low on the outer peripheral side. Therefore, when the additional gas is a gas having a temperature higher than the intake temperature such as EGR gas or blow-by gas, the temperature distribution of the mixture of the intake gas and the additional gas in the curved portion is
The inner circumference is high and the outer circumference is low. Therefore, although the fuel injected from the injector is originally hard to adhere to the inner peripheral wall surface of the curved portion due to the arrangement structure of the injector as described above, a part thereof still reaches the inner peripheral wall surface. However, in this case, even if the fuel reaches the inner peripheral wall surface side, the temperature of the air-fuel mixture in this part is relatively high, and the inner peripheral wall surface itself is warmed by the additional gas, so that the wall temperature is high. From that,
The fuel is quickly vaporized here, and it is almost impossible to adhere and remain on the inner peripheral wall surface.

According to the second aspect of the present invention, since the injection hole of the injector is opened on the outer peripheral side of the curved portion, the fuel from the injector is injected into the maximum flow velocity region in the curved portion. As a result, the mixing of the fuel and the intake air is made good, the vaporization and atomization of the fuel are promoted, and the adhesion of the fuel to the inner peripheral wall surface is suppressed as much as possible. In this case, since the opening / closing valve configured by the butterfly valve has its opening direction set such that the peripheral portion near the outer periphery of the curved portion is located on the intake downstream side when the opening / closing valve is opened, When the intake air on the upstream side passes through the opening / closing valve portion, it is guided by the opening / closing valve and is biased toward the outer peripheral side of the curved portion. For this reason, the biased flow action of the on-off valve further increases the bias of the flow velocity distribution due to the secondary flow, the maximum flow velocity of the intake air flow in the bending portion is further increased, and the injection hole of the injector is changed to the bending portion. By arranging it near the outer periphery, the mixing action of fuel and intake air is further promoted.

Further, since the on-off valve is a butterfly valve, even if the on-off valve is fully closed, the intake air passes through a minute gap between the outer peripheral edge of the on-off valve and the passage wall. Will leak to the downstream side of the on-off valve.
Further, since this on-off valve is arranged near the upstream end of the bending portion, compared with the case where this on-off valve is arranged near the downstream end of the bending portion as in the conventional case, the intake air from the on-off valve is increased. The distance between the ports becomes longer, and the volume between the on-off valve and the intake port increases accordingly. Therefore, the amount of intake air that leaks from the on-off valve and accumulates in the volume between the on-off valve and the intake valve becomes larger than that of the conventional structure, and as a result, the intake valve and the exhaust valve are exhausted in the final stage of the exhaust process. If the valve opening of the valve overlaps, a large amount of intake air that has accumulated in the volume will flow into the combustion chamber side and will be discharged from the exhaust port while scavenging the vicinity of the exhaust valve. The scavenging action is promoted only by the large amount of residual intake air.

In the invention according to claim 3, the intake passage is composed of the upstream side curved portion, the straight line portion, and the downstream side curved portion,
Since the injection hole of the injector is arranged at the outer peripheral portion of the upstream curved portion and the additional gas ejection portion is opened at the inner peripheral portion thereof, the intake flow in the upstream curved portion is increased. Regarding the above, it goes without saying that the same action as described above can be obtained, but in addition to this, the following action can also be obtained. That is, the straight line portion is continuous with the downstream end of the upstream side bend portion and linearly extends obliquely downward, and the downstream side bendable portion is continuous with the downstream end of the straight line portion in a direction opposite to the upstream side bend portion. Since it is curved to (in other words, curved so as to be directed in the axial direction of the combustion chamber), the mixed air flow introduced into the combustion chamber from the downstream bending portion via the straight portion from the upstream bending portion, A tumble flow that swirls in the vertical direction is generated in the combustion chamber.

In this case, since the bending directions of the upstream bending portion and the downstream bending portion are opposite to each other, the additional gas located on the inner peripheral side of the upstream bending portion bends in the downstream bending portion. The part is located on the outer peripheral side.
Therefore, when the additional gas is introduced into the combustion chamber from the straight line portion, it is located on the outer peripheral side of the intake flow and is introduced into the combustion chamber in that state to form a tumble flow,
In the combustion chamber, the additional gas layer is unevenly distributed in a relatively low temperature portion such as the combustion chamber wall surface or the piston top surface, and the intake air is a relatively rich mixture inside the additional gas layer (that is, It will be biased toward the center of the combustion chamber).

As a result, stratification in the combustion chamber is promoted, lean combustion is realized, and especially when a flame-retardant gas such as EGR gas or blow-by gas is used as the additional gas, the temperature is low and the unburned components are unburned. Since the part that is likely to be the place where is generated is covered by the flame-retardant gas and the intrusion of the air-fuel mixture into this part is suppressed, the generation of unburned component itself is suppressed as much as possible, and the exhaust emission is good. Will be

According to a fourth aspect of the present invention, the intake passage is composed of an upstream curved portion, a straight portion, and a downstream curved portion,
2. The invention according to claim 1, wherein the injection hole of the injector is opened on the outer peripheral side of the upstream curved portion, and the injection portion of the additional gas is opened on the inner peripheral side of the upstream curved portion. It has a configuration in which the invention described in Item 3 is combined, and therefore, the above-described operation and the above-described operation can be achieved at the same time.

According to the fifth aspect of the present invention, the injection hole of the injector is opened on the outer peripheral side of the curved portion of the intake passage, and the injection portion of the additional gas is opened on the inner peripheral side thereof. An on-off valve is arranged, which has a configuration in which the invention described in claim 1 and the invention described in claim 2 are combined, so that the above-described operation and the above-described operation can be achieved at the same time. It is a thing.

According to a sixth aspect of the present invention, the intake passage is composed of the upstream curved portion, the straight portion, and the downstream curved portion, and the injector injection hole is formed on the outer peripheral side of the upstream curved portion. And a switching valve disposed near the upstream end of the upstream curved portion, the combination of the invention according to claim 2 and the invention according to claim 3. Therefore, it is possible to achieve the above-mentioned action and the above-mentioned action at the same time.

The invention according to claim 7 is the invention according to claim 1, 3,
In the invention described in 4, 5, or 6, in addition to an additional gas passage for supplying an additional gas, an assist air passage for supplying assist air is provided, and each of these passages is arranged so as to straddle the intake passage of each cylinder. It is needless to say that the above-mentioned ,,, or the above-mentioned effects can be obtained from the fact that it is formed by the above-mentioned structure, but in addition to that, the intake passages are integrally connected by the additional gas passage and the assist air passage. Therefore, the rigidity of these is increased.

[0032]

Therefore, according to the engine intake system of each invention of the present application, the following effects are obtained.

(A) According to the engine intake device of the first aspect, the injection hole of the injector is opened on the outer peripheral side of the curved portion of the intake passage to inject and supply the fuel toward the maximum flow velocity range. The mixing of fuel and intake air can be improved to further promote the vaporization and atomization of the fuel, and the adhesion of the fuel to the inner wall surface can be prevented to improve the responsiveness of the engine output to the fuel supply. It is possible.

Furthermore, since the average flow velocity in the intake passage is increased by introducing the additional gas to the inner peripheral side of the curved portion, the utilization efficiency of the effective cross-sectional area of the intake passage is improved accordingly, resulting in the filling efficiency. Can be improved. That is, although the intake passage having a curved structure is provided, promotion of vaporization and atomization of fuel by maintaining a high maximum flow velocity and improvement of filling efficiency by maintaining a high average flow velocity are achieved at the same time. Is something that can be done.

(B) According to the engine intake device of the second aspect, the flow velocity distribution of the intake air peculiar to the intake passage having the curved portion is caused by the uneven flow of the intake air by the opening / closing valve arranged near the upstream end of the curved portion. By further increasing the bias of (1) and further increasing the maximum flow velocity, the vaporization and atomization of fuel can be further improved as compared with the case described in (a) above.

Further, the on-off valve is arranged near the upstream end of the bending portion to increase the volume between the on-off valve and the intake port, and to prevent the intake air leaking from the periphery of the on-off valve into this volume. Since a large amount of air is stored and the intake port and the exhaust valve overlap when the opening timings of the intake valve and the exhaust valve overlap, the surroundings of the exhaust port are scavenged by a large amount of intake air.
The scavenging performance is high, and the intake charge amount can be increased accordingly.

(C) According to the engine intake device of the third aspect, in addition to the effect of the above (a), the intake passage is composed of the upstream curved portion, the straight portion, and the downstream curved portion. As a result, a tumble flow is generated in the combustion chamber, and an additional gas is present on the outer peripheral side of this tumble flow and a mixture is present in layers on the inner peripheral side to stratify the mixture. It is possible to improve fuel efficiency.

Further, since the additional gas is allowed to exist at the outer peripheral portion of the combustion chamber having a relatively low temperature, that is, at the place where the unburned component is generated, the mixture itself is prevented from entering the portion. It also has the effect of reducing the amount of components produced as much as possible and improving the exhaust emission of the engine.

(D) According to the engine intake device of the fourth aspect, the same effects as those described in the above (a) and (c) can be achieved at the same time.

(E) According to the engine intake device of the fifth aspect, the effects described in (a) and (b) above can be achieved at the same time.

(F) According to the engine intake device of the sixth aspect, the effects of the above (b) and (c) can be achieved at the same time.

(G) According to the engine intake device of claim 7, in addition to the effect described in (a), (c), (d), (e) or (f), it corresponds to each cylinder. Since the respective intake passages are integrally connected by the additional gas passage and the assist air passage, the rigidity between the respective intake passages is improved, and by extension, the rigidity of the engine as a whole is increased. It is possible to obtain an effect that noise generation due to vibration can be reduced.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An intake system for an engine according to the present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. FIG. 1 and FIG. One bank portion of a V-type engine is shown. In the figure, reference numeral 1 is a cylinder block, 2 is a cylinder head, and 3 and 4 are a pair of left and right camshafts 2.
A cam carrier that supports 3, 24, 5 is a head cover,
6 is a piston and 7 is a combustion chamber. This engine is an intake two-valve / exhaust two-valve engine, and intake ports 8 and 8 are provided on the lower surface of the cylinder head 2 facing the combustion chamber 7.
And exhaust ports 9 and 9, respectively, and further, intake valves 20 and 20 are respectively provided to the intake ports 8 and 8, and exhaust valves 21 and 21 are provided to the exhaust ports 9 and 9, respectively. Are arranged.

Further, in this engine, the pair of intake ports 8 and 8 are connected to the surge tank 17 arranged above the head cover 5 via the independent primary passage 11 and secondary passage 12. The two passages 11 and 12 constitute the intake passage 10 corresponding to one cylinder. Further, of the two passages 11 and 12, the primary passage 11 introduces intake air in the entire operating region of the engine, while the secondary passage 12 introduces intake air only in a high load region where the engine load is equal to or higher than a predetermined value. The primary passage 11 and the secondary passage 12 are provided with an on-off valve 18 described later at the most upstream position of the secondary passage 12 (that is, the outlet portion 17a of the surge tank 17).
1 has the same configuration as that of FIG. 1 except that a blow-by gas ejection portion 36 as additional gas is formed at an intermediate position of the secondary passage 12.
3 to 4, only the passage structure of the secondary passage 12 will be described in detail, and the description of the passage structure of the primary passage 11 will be omitted.

The secondary passage 12 is connected to the intake port 8 so as to be directed upward in the cylinder head 2 and is gradually curved toward the side of the engine. 15, a straight line portion 14 extending linearly in a diagonally upward direction on the upstream side of the cylinder head 2 and having an upstream end opening to a side surface of the cylinder head 2, an upstream end of the straight line portion 14 and the surge. Tank 17
The upstream bending portion 13 which is detachably arranged across the outlet portion 17a of the engine and bends in the opposite direction to the downstream bending portion 15 so that the upper end of the engine is wound from the side thereof.
It consists of and. And this secondary passage 1
The outlet section 1 of the surge tank 17 which is the uppermost stream position of No. 2
An opening / closing valve 18 constituted by a butterfly valve is located at 7a and has its valve shaft 19 oriented in a direction orthogonal to the curved surface of the upstream bending portion 13 and located near the outer peripheral wall 13a of the upstream bending portion 13. The peripheral edge portion 18a is positioned downstream of the valve shaft 19 and is disposed.

As shown in FIG. 2, the upstream bending portion 13 has the upstream bending portion 2 on the primary passage 11 side.
2 (see FIGS. 2 and 3) and is integrally formed in parallel with each other, and is connected to each other by a pair of upper and lower flanges 41, 42 between the intake passages 10, 10 of each cylinder. The intake manifold 30 is configured.

Further, as shown in FIGS. 1 and 3, in the vicinity of the downstream end of the upstream curved portion 13 and near the outer peripheral wall 13a, injection holes for introducing fuel into the upstream curved portion 13 are provided. 26, the intake port 8 through the straight portion 14.
Is formed so as to be directed to
An injector 25 is disposed on the upstream end side of the.
The injection hole 26 is also formed in the upstream curved portion 22 of the primary passage 11 in the same manner, and the fuel injected from the injector 25 passes through the two injection holes 26, 26 and is discharged to the primary side. It is designed to be supplied to both the passage 11 side and the secondary passage 12 side at the same time.

On the other hand, the intake manifold 30 is shown in FIG.
And, as shown in FIG. 2, the blow-by gas passage 3 is formed inside the inner peripheral wall 13b of the upstream side curved portion 13 at a position outside thereof.
5 and the assist air passage 37 are provided side by side
The intake passages 10, 10, 10 of the respective cylinders are integrally formed in a state of straddling in the lateral direction. The blow-by gas passage 35 is opened on the inner peripheral wall 13b on the upstream side of the injection hole 26 through the ejection portion 36 formed by penetrating the inner peripheral wall 13b of the upstream side curved portion 13. The blow-by gas G (corresponding to the additional gas in the claims) introduced from the exhaust passage 16 side is branched to each cylinder side by the blow-by gas passage 35, and the jet portions 36, 36 ,. Are introduced into the secondary passages 12 of the corresponding cylinders. Further, the assist air passage 37 is communicated with the most upstream portion of the injection hole 26 through a communication passage 38 formed in the intake manifold 30, and the assist air supplied to the assist air passage 37 is communicated. Is divided into the respective cylinders and then supplied from the communication passage 38 to the most upstream portion of the injection hole 26.

Next, with respect to the operation and effects of the intake system thus constructed, mainly the secondary passage 1 will be described.
The flow on the second side will be described as an example. When the engine is operated, first, the open / close valve 18 is kept closed in the low load region, so the intake air is introduced into the combustion chamber 7 only from the primary passage 11 side, and the swirl flow is generated in the combustion chamber 7. Occur. Further, in this case, the fuel is diverted from the injector 25 to both the primary passage 11 and the secondary passage 12, so that the mixture of intake air and fuel is discharged from the primary passage 11 side, and the fuel is mixed from the secondary passage 12 side. Only fuel is introduced respectively.
Further, separately from this, the assist air supplied to the assist air passage 37 passes through the communication passage 38 and is injected into the injector.
It is supplied to the vicinity of the 25 nozzles to promote the mixing of fuel and intake air and to vaporize and atomize the fuel. Further, the blow-by gas supplied to the blow-by gas passage 35 is blown out by the ejection portion 3
6 is introduced into the upstream curved portion 13 of the secondary passage 12 (accordingly, strictly speaking, the mixture of blow-by gas and fuel is introduced into the combustion chamber 7 from the secondary passage 12). Become).

On the other hand, when the engine load increases and reaches the high load operation range, the opening / closing valve 18 is opened, so that the primary passage 11 and the secondary passage 1 are provided in the combustion chamber 7.
A mixture of intake air and fuel is introduced from both of the two. Separately from this, blow-by gas is introduced into the upstream curved portion 13 of the secondary passage 12 from the ejection portion 36.

Here, the flow of intake air and blow-by gas in the secondary passage 12 and the mixing action of fuel in this case will be described. First, regarding the flow of intake air, the intake air flows from the surge tank 17 through the opening / closing valve 18 to the secondary passage 12 side, and then flows through the secondary passage 12 from the upstream curved portion 13 to the straight portion 14 to the downstream side. It reaches the curved portion 15 and is finally sucked into the combustion chamber 7 from the intake port 8. In this case, since the upstream bending portion 13 is largely bent, the upstream bending portion 1 is caused by the secondary flow due to the inertial force of the intake air flow.
The velocity distribution in 3 is the velocity distribution curve L ₁ in FIG.
As shown by, the maximum flow velocity is biased toward the outer peripheral wall 13a. The deviation of the flow velocity distribution becomes most remarkable when the opening / closing valve 18 is opened. That is, since the opening / closing valve 18 is opened so that the outer peripheral edge 18a near the outer periphery of the curved portion is located on the intake downstream side, the intake air from the surge tank 17 passes through the opening / closing valve 18. This is because the on-off valve 18 acts to bias the flow toward the outer circumference of the curved portion. Therefore, in this case the highest maximum flow rate is achieved.

With the conventional structure, such a biased flow velocity distribution is maintained as it is while the intake air is flowing through the upstream bending portion 13, but in this embodiment, the upstream bending portion 13 has the same flow velocity distribution. Since the jet portion 36 is formed on the inner peripheral wall surface 13b in the middle of the passage and the blow-by gas is introduced into the upstream bending portion 13 from here,
The flow velocity distribution gradually changes as the intake air flows down.

That is, on the upstream side of the jet portion 36, there is a flow velocity distribution as shown by the flow velocity distribution curve L ₁ in FIG. 4, and therefore, in the vicinity of the inner peripheral wall surface 13b of the upstream side curved portion 13, the dynamic pressure due to the intake flow A is generated. Is low, and the blow-by gas G is smoothly introduced into the upstream side curved portion 13 from here.
The blow-by gas G introduced in the vicinity of the inner peripheral wall surface 13b is pushed to the downstream side by the intake air flow in the upstream side curved portion 13 as it is, and becomes a form added to the intake air flow A, resulting in ejection. Immediately downstream of the portion 36, as shown by the flow velocity distribution curve L ₂ in FIG. 4, a "two-hump camel" shape having high flow velocity regions at both the outer wall surface 13a and inner wall surface 13b positions. The flow velocity distribution becomes.

However, such a "two-hump camel" -shaped flow velocity distribution does not last forever, and the high flow velocity region near the inner peripheral wall surface 13b is gradually affected by the secondary flow as the intake air flows down. It is extruded to the outer peripheral wall surface 13a side, and exhibits a substantially trapezoidal flow velocity distribution with no significant difference in flow velocity between the outer peripheral wall surface 13a and the inner peripheral wall surface 13b, as shown by the flow velocity distribution curve L ₃ in FIG.
Therefore, under such a flow velocity distribution,
The maximum flow velocity at the position close to the outer peripheral wall surface 13a hardly changes, while the average flow velocity in the upstream curved portion 13 increases significantly. The increase of the average flow velocity in this manner increases the cross-sectional area of the upstream side curved portion 13 that can effectively contribute to the intake air introduction (in other words,
The utilization efficiency of the effective cross-sectional area is increased), so that a large amount of intake air can be introduced at a high speed, and as a result, the charging efficiency of intake air is improved, which in turn leads to improved output performance. Incidentally, when the flow velocity distribution on the downstream side of the blow-by gas ejection portion 36 is improved in this way, this effect does not stop only on the downstream side, and the ejection portion 36
It goes without saying that the flow velocity distribution in that portion is also improved by extending to the upstream side.

The high flow velocity region near the inner peripheral wall surface 13b, which is achieved by the addition of blow-by gas, gradually moves toward the outer peripheral wall surface 13a as the intake air flows down, so that the blow-by gas ejection portion 36 is formed to some extent. The flow velocity distribution is such that the highest average flow velocity as shown by the flow velocity distribution curve L ₃ in FIG. 4 is obtained at a position near the downstream side, and as it goes further downstream, the bias of the flow velocity distribution toward the outer peripheral wall surface 13a side becomes noticeable again. Then, finally, only the maximum flow velocity has a prominent flow velocity distribution, which is not desirable in terms of filling efficiency. Therefore, in this embodiment, the downstream end position of the upstream curved portion 13 is set in the vicinity of a position where a flow velocity distribution such as the flow velocity distribution curve L ₃ of FIG. 4 is obtained, and the injector 25 is provided at this position. The injection hole 26 is opened.

On the other hand, the fuel injected from the injector 25 has a nozzle hole 2 which is opened at a position where a flow velocity distribution such as the above-mentioned flow velocity distribution curve L ₃ can be obtained and near the outer peripheral wall surface 13a.
Since the fuel is supplied from 6 toward the axial direction of the linear portion 14, the fuel rides on the intake air of the portion having the largest flow velocity, and mixing with the intake air is promoted.
The atomized state can be made as good as possible, which can contribute to the improvement of the combustion performance of the engine.

Looking at the flow of the blow-by gas, the blow-by gas is gradually moved to the outer peripheral wall surface 13a side by the secondary flow as it is introduced into the upstream side curved portion 13. Outer wall 1
It does not mean that it moves to the 3a side, but that it gradually moves while mixing with intake air. Therefore, when viewed from the entire flow in the secondary passage 12, the upstream bending portion 1
Blow-by gas G introduced to the inner peripheral wall surface 13b of No. 3
The density distribution in the secondary passage 12 is still high on the inner wall surface 13b side and low on the outer wall surface 13a side up to its downstream end (that is, the intake port 8). Therefore, the intake air temperature from the vicinity of the downstream end of the upstream curved portion 13 to the straight portion 14 (strictly speaking, the temperature of the air-fuel mixture of intake air and blow-by gas) is a portion near the inner wall surface 13b of the upstream curved portion 13. Is higher, and so is the wall temperature.

Therefore, the fuel injected from the injection hole 26 into the upstream curved portion 13 rides on the intake flow of high velocity and flows into the combustion chamber 7.
And the temperature (both the wall temperature and the ambient temperature) is high on the side of the inner peripheral wall surface 13a and the vaporization and atomization properties of the fuel in this portion are good, so that the inner peripheral wall surface 13b Side wall surface (straight portion 14 and downstream curved portion 15
(Including the wall surface of the fuel cell) is prevented as much as possible, and the response of the engine output to fuel control is improved.

Further, in the secondary passage 12, as described above, mainly intake air flows in the portion near the outer peripheral wall surface 13a of the upstream side curved portion 13, and blowby gas mainly flows in the inner peripheral wall surface 13b side. As shown in the example, the straight portion 14 has a considerably large inclination and the intake port
And the downstream side curved portion 1 following this.
When 5 is curved in the axial direction of the combustion chamber 7, the air-fuel mixture sucked from the intake port 8 into the combustion chamber 7 is
A so-called tumble flow that swirls in the vertical direction is generated inside. By the way, in this embodiment, the blow-by gas G mainly existing near the inner peripheral wall surface 13b of the upstream side curved portion 13 as described above remains as it is.
The wall surface of the straight portion 14 located on the 3b side and the downstream bending portion 1
Since it flows into the combustion chamber 7 along the wall surface of 5, the blow-by gas G exists in layers inside the combustion chamber 7 near the inner wall of the combustion chamber 7 or the top surface of the piston 6.
The air-fuel mixture B of the intake air and the fuel exists in a state of being enclosed inside the blow-by gas layer. That is, stratification in the combustion chamber 7 is achieved.

Therefore, it is needless to say that the fuel ratio performance is improved by realizing lean combustion by stratifying the air-fuel mixture, but in addition to this, the exhaust emission and knocking performance are also improved at the same time. That is, since the non-combustible gas called blow-by gas occupies the outer peripheral portion of the combustion chamber 7, that is, the portion where unburned components are likely to be generated due to poor combustion due to the relatively low temperature, the air-fuel mixture to this portion There is no inflow, and therefore, naturally, no combustion occurs in this portion, and as a result, generation of unburned components themselves is suppressed as much as possible, which leads to improvement of exhaust emission. Further, the fact that the outer peripheral portion of the combustion chamber 7 is occupied by the blow-by gas in this manner eliminates the end gas zone itself, which is a cause of knocking, which is a cause of knocking. Is expected to improve output performance by increasing the compression ratio.

Further, in the low load region of the engine, the on-off valve 18 is kept closed, but since the on-off valve 18 is composed of a butterfly valve, even if it is in a fully closed state, A minute gap is formed between the peripheral edge and the passage wall. Therefore, when the open / close valve 18 is closed, the intake air leaks little by little from this gap to the intake port 8 side. On the other hand, this on-off valve 18
Conventionally, it is generally arranged at a position close to the intake port 8,
In this embodiment, since it is arranged in the vicinity of the upstream end of the upstream side curved portion 13, the volume between the on-off valve 18 and the intake valve 20 is considerably larger than that of the conventional structure. The amount of intake air that leaks from the gap of the on-off valve 18 and accumulates in this volume also increases significantly. As described above, when a large amount of intake air is accumulated in the volume, a large amount of intake air is introduced from the intake port 8 into the combustion chamber 7 when the intake valve 20 and the exhaust valve 21 are opened in the final stage of the exhaust stroke. Intake air flows in, and the inflow intake air effectively scavenges the vicinity of the exhaust port 9.

Further, since the blow-by gas passage 35 and the assist air passage 37 are juxtaposed in the laterally-arranging portion 31 in a close state, the assist air in the assist air passage 37 is warmed by the heat of the blow-by gas. After that, since the fuel is supplied to the vicinity of the injection port of the injector 25, the action of promoting the vaporization and atomization of the fuel by the assist air is further enhanced. In addition, the horizontal installation portion 31 forming the blow-by gas passage 35 and the assist air passage 37 is
Since the intake manifold 30 is formed so as to straddle the intake passages 10, 10, ... In the cylinder arrangement direction, the intake manifold 30 is connected at its upper and lower ends by flanges 41, 42, respectively. in addition,
Since the intermediate portion is also connected by the laterally-provided portion 31, its rigidity is improved. And
By increasing the rigidity of the intake manifold 30, the rigidity of the engine as a whole is increased, and noise generation due to engine vibration is reduced as much as possible.

In the above embodiment, the blow-by gas is introduced as the additional gas, but the present invention is not limited to this. For example, the blow-by gas may be replaced with the EGR gas as the additional gas. It can also be adopted.

Further, in this embodiment, the spouting portion 36 of the additional gas is formed on the side of the secondary passage 12, but the present invention is not limited to this. For example, it is formed on the side of the primary passage 11. It can also be done.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an engine including an intake device according to an embodiment of the present invention.

FIG. 2 is a view taken along the line II-II in FIG.

3 is a vertical sectional view taken along the line III-III in FIG.

FIG. 4 is an explanatory diagram of a flow velocity distribution of intake air in an intake passage.

FIG. 5 is an explanatory diagram of a flow velocity distribution of intake air in an intake passage.

[Explanation of symbols]

1 is a cylinder block, 2 is a cylinder head, 3 is a cam carrier, 4 is a cam carrier, 5 is a head cover, 6 is a piston, 7 is a combustion chamber, 8 is an intake port, and 9 is an exhaust port.
10 is an intake passage, 11 is a primary passage, 12 is a secondary passage, 13 is an upstream curved portion, 14 is a straight portion, 15 is a downstream curved portion, 16 is an exhaust passage, 17 is a surge tank, 18 is an opening / closing valve. , 19 is a valve shaft, 20 is an intake valve,
Reference numeral 21 is an exhaust valve, 23 is a cam shaft, 24 is a cam shaft, 25 is an injector, 26 is an injection hole, 30 is an intake manifold, 31 is a laterally installed portion, 35 is a blow-by gas passage, 36 is an ejection portion, and 37 is an assist. It is an air passage.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display area F02M 29/00 C 8923-3G 69/04 P 9248-3G G 9248-3G

Claims (7)

[Claims] 1. In an intake system of an engine, wherein an injector is arranged in an intake passage having a curved portion and an appropriate additional gas is supplied into the intake passage, an injection hole of the injector is provided in the intake passage. Of the additional gas is opened on the wall surface of the curved portion or the position immediately downstream of the curved portion and on the outer peripheral side of the curved portion, while the injection portion of the additional gas is opened on the inner wall surface of the curved portion. An engine intake device characterized by the above. 2. An intake air of an engine, wherein an injector is arranged in an intake passage having a curved portion, and an on-off valve which selectively opens and closes the intake passage according to an operating state of the engine is provided upstream of the injector. In the device, the injection hole of the injector is opened on the wall surface on the outer peripheral side of the curved portion, while the on-off valve is constituted by a butterfly valve and its valve axis direction is orthogonal to the curved surface direction of the curved portion. Is arranged in the vicinity of the upstream end of the bending portion in a state of being directed toward the intake side, and when the valve is opened, the peripheral portion located on the outer peripheral side of the bending portion is on the intake downstream side of the peripheral portion located on the inner peripheral side. An intake device for an engine, wherein a valve opening operation direction is set to be located at. 3. An intake device for an engine, wherein an injector is arranged in the intake passage and an appropriate additional gas is supplied into the intake passage,
An upstream side curved portion located upstream of the engine and curved so as to wrap around from the upper side to the side of the engine; and a straight line portion that linearly extends obliquely downward continuously to the downstream end of the upstream side curved portion, and the straight line. A downstream side curved portion which is continuous to the downstream end of the portion and which is curved in the opposite direction to the upstream side curved portion and communicates with the intake port, while the injector injection hole of the injector is An intake device for an engine, characterized in that the additional gas is ejected onto an inner peripheral side wall surface of the upstream curved portion while the axial extension is opened. 4. An intake system for an engine, wherein an injector is arranged in the intake passage and an appropriate additional gas is supplied into the intake passage, the intake passage comprising:
An upstream curving portion located upstream of the engine and curving so as to wrap around from the upper side to the lateral side of the engine, a linear portion continuously linearly extending from a downstream end of the upstream curving portion, and a downstream portion of the linear portion. And a downstream side curved portion which is continuous to the end and which is curved in a direction opposite to the upstream side curved portion and communicates with the intake port. Further, the injection hole of the injector is provided with the upstream side curved portion or the straight line. The opening of the additional gas is opened on the wall surface corresponding to the outer peripheral side of the upstream curved portion, and the ejection portion of the additional gas is opened on the wall surface corresponding to the inner peripheral side of the upstream curved portion. The intake system of the engine. 5. An injector is arranged in an intake passage having a curved portion so that an appropriate additional gas can be supplied into the intake passage, and an engine operating state is provided upstream of the injector. In an intake system for an engine in which an opening / closing valve for selectively opening / closing the intake passage is arranged, the injection hole of the injector is provided at a curved portion of the intake passage or at a position immediately downstream of the curved portion and at the outer periphery of the curved portion. On the inner side wall surface of the curved portion, and the opening / closing valve is constituted by a butterfly valve and the valve axis direction thereof is the curved portion. The bending portion is arranged and set in the vicinity of the upstream end of the bending portion in a direction orthogonal to the bending surface direction, and when the valve is opened, the peripheral portion located on the outer peripheral side of the bending portion is located on the inner peripheral side. You An intake system for an engine, wherein a valve opening operation direction is set so as to be located on a downstream side of intake air with respect to a peripheral portion thereof. 6. An injector is arranged in the intake passage so that an appropriate additional gas can be supplied into the intake passage, and the intake passage is selected upstream of the injector according to the operating condition of the engine. In an intake system for an engine having an opening / closing valve that opens and closes dynamically, an upstream bending portion that is located upstream of the intake passage and bends so as to wrap around from the upper side to the side of the engine, and the upstream bending portion. A straight line portion continuously extending to the downstream end of the straight line portion, and a downstream side curved portion which is continuous to the downstream end of the straight line portion and which curves in a direction opposite to the upstream side curved portion and communicates with the intake port. On the other hand, while the injection hole of the injector is opened on the axial extension of the straight portion, the injection portion of the additional gas is opened on the inner peripheral side wall surface of the upstream curved portion.
Further, the on-off valve is configured by a butterfly valve and is arranged and set in the vicinity of the upstream end of the bending portion with the valve axis direction thereof being directed in a direction orthogonal to the bending surface direction of the bending portion, and the valve opening thereof is performed. An intake device for an engine, wherein the valve opening operation direction is set so that a peripheral edge portion located on the outer peripheral side of the curved portion is located on the intake downstream side with respect to a peripheral edge portion located on the inner peripheral side at the time. 7. The intake system for an engine according to claim 1, 3.4, 5 or 6, wherein assist air can be supplied to the vicinity of the injection hole of the injector through an assist air passage, and the addition is possible. An additional gas passage for supplying gas is arranged in parallel near the assist air passage, and the assist air passage and the additional gas passage are formed so as to straddle the intake passages of each cylinder. And the intake system of the engine.